Wednesday, December 30, 2009

Environment Canada's Dave Phillips released his Top 10 weather stories of 2009 list today.. an annual look at the top weather events across Canada. The number one story was the "summer of our discontent", a summer which was too cool and wet for most, too hot and dry in BC. Other top weather stories were the record ice-jam flooding on the Red, the Toronto area tornado outbreak, and the prolonged 9 month spell of below normal temperatures in the Prairies. What do you think was the top weather story for Winnipeg in 2009? Cast your vote on my blog poll! Say goodbye to 2009.. here's looking to a warm and pleasant 2010!

Friday, December 25, 2009

The next wave of snow from a strong winter storm system over Iowa is spreading over southern MB this morning from the southeast. Visibilities will be lowering through the day as gusty north winds to 50 or 60 km/h combine with falling and fresh snow to produce blowing and drifting snow. This will make for poor travelling conditions today into tonight across southern MB highways, especially through the Red River valley (see Pembina webcam for latest conditions). Travel is not advised this morning across most ND highways and a few over southern MB. Consult MB highways and ND highways for latest road information.

Thursday, December 24, 2009

Those hoping for snow for Christmas are getting their wish.. snowfall has begun over southern MB today, and will likely continue through Friday before tapering off Saturday. The snow today is the initial wave of the storm system being supported by a trough of low pressure moving in from Saskatchewan. This first wave of snow will bring about 2-8 cm of snow to southern MB today before it dissipates later today into this evening. Another round of snow will move in by Christmas morning from the south as the strong winter storm system pushing into Iowa spreads a large area of precipitation northward. This next wave will likely bring another 5-15 cm of snow to southern MB with the highest amounts near the US border. In addition winds will be increasing Friday from the north which will give reduced visibilities in snow and blowing snow resulting in poor travelling conditions for Christmas day. All told, snowfall totals over the next couple of days will range from 10-15 cm in Winnipeg to 25 cm over the southern and western Red River valley. Note that winter storm and blizzard warnings have been posted for parts of North Dakota and Minnesota due to this storm system.

Monday, December 21, 2009

A storm system is forecast to develop over the southern Plain states Tuesday into Wednesday, which will then move northeast and intensify into a strong winter storm Thursday into Christmas Day. Current indications are this storm will track from northern Texas into Wisconsin by Friday, with heavy snow and strong winds likely west of the storm track over portions of South Dakota, Nebraska, Iowa and Minnesota. A messy mix of freezing rain and ice pellets is possible along and east of the storm track. Snow from this system may extend into North Dakota and southern MB as well by Christmas Eve, although currently the worst of it is expected to stay southeast of us. Stay tuned on this developing situation especially if you have travel plans south or east of Manitoba for the holidays.

UPDATE: Dec 22: Winter storm watches have been posted for all of North Dakota and Minnesota right to the Canadian border for the potential of heavy snow beginning Wednesday and continuing through Christmas Day. Latest guidance indicates some snow will be moving into southern MB from this system as well Thursday into Friday although the heaviest amounts are still expected south of the border. Stay tuned..

Saturday, December 19, 2009

After the 2nd driest November on record with only 1.5 mm of melted snow for the month, the dry weather pattern has continued into December. As of the 18th, only 1.0 mm of melted snow has been recorded at Winnipeg airport this month, with a meager snowcover of 2 cm on the ground. This is the thinnest snow cover in Winnipeg for this time of year since 2002 when no snow was on the ground as of the 18th. And unfortunately for snowlovers out there, prospects for any significant snowfall over southern MB look low over the next week. A weak system passing through southern MB tonight into Sunday may bring a dusting to 2 cm, but overall it looks dry over the upcoming week with no major snowfalls forecast for southern MB through Christmas. That's good news for those with holiday travel plans this week, but not the best news for those looking for some nice powder for snowmobiling or skiing. Long range models are forecasting a strong storm system developing over the southern US Plains moving into the Great Lakes mid to late next week, but it appears this system will stay well to our south and east. In the meantime, those wishing for snow will have to look with envy to the US East Coast this weekend where a strong nor'easter is expected to bring 20-50 cm of heavy snow from Washington DC to Boston.

Wednesday, December 16, 2009

After several days of Arctic cold, temperatures will finally be moderating over southern MB over the next few days. A warm front will be pushing across southern MB tonight bringing clouds and a possibility of some snow (dusting to 2 cm) . This front will keep temperatures from dropping tonight, and will usher in temperatures in the minus single digits Thursday for the first time since December 6th. Slightly colder weather is forecast for Friday into the weekend although temperatures should be close to normal for this time of year (normal highs minus 11, normal lows minus 20)

Monday, December 14, 2009

This recent cold spell has once again shown that people (especially the media!) are often confusing windchill with an actual temperature. This appeared in an article today in the Toronto Sun - "The Edmonton International Airport recorded a low of -46.1C, with the mercury dropping to -58.4C with the windchill, outfreezing even the Arctic." Well, that's not exactly true. The mercury did indeed drop to -46.1C at Edmonton airport, but it never dropped to -58.4C. That was the windchill factor which isn't a temperature at all, but rather a value that estimates the cooling rate of the air given a certain temperature and wind speed. With no wind, your body will lose heat at a certain rate depending on the air temperature. If there's a wind, your body will lose heat at a faster rate because the wind erodes the warm insulating layer near your skin that keeps in heat. The faster the wind, the faster the heat loss, and the "colder" it feels since your body feels like it's losing heat at the same rate as a colder temperature.

For example, let's say it takes 20 minutes for you to feel cold when it's -25C outside and no wind. And let's say it takes you 10 minutes to feel cold when it's -40C with no wind. Now, let's say it's -25C with a 30 km/h wind. Because of the wind, your body starts losing heat more quickly, and you start feeling cold after only 10 minutes. Your body will tell you, hey it must be -40C out here because it took 10 minutes for you to start feeling cold. But is it -40C outside? No, it's -25C. To you, it just feels like -40C because of the wind that accelerated your body's heat loss. People will say it "feels like" -40 with the windchill.. which is a way of saying that the wind makes it feel colder than it actually is.

Because of this, windchill should never be stated as a temperature value (like degrees C).. it really should be expressed as a cooling rate (e.g. -58.4CU "cooling units") but in Canada, it's officially displayed without any units. Media has become overly fascinated with the windchill (I guess because it sounds so much worse than the actual temperature!) to the point that often they're just giving windchill values instead of the actual air temperature! The problem with this is that people start quoting windchill values as actual temperatures (as in the Sun article), which they are not.

Temperature is a measure of how much heat energy a parcel of air holds. The more heat energy, the higher the temperature. Windchill on the other hand is an index that estimates the RATE of energy loss of an air parcel given its original heat energy AND a prevailing wind that helps to accelerate the amount of energy leaving the air parcel (i.e. cooling rate). So, temperature is the amount of heat energy an air parcel has.. windchill is the rate of cooling of that air parcel.

Look at it this way... You have a bucket of water at +5C. You put it outside, where the air temperature is a constant +2C, but a wind of 50 km/h is producing a windchill of -5. Will that bucket of water freeze? Of course not. The water will only cool down to the ambient air temperature.. +2C. It can't get any colder than its environment unless it's cooled by some other method (e.g. refrigeration) The windchill of -5 merely implies that the water will cool down to +2C at a rate equivalent to that if the water was outside at -5C with no wind. So instead of taking one hour to cool down to +2C, it will only take 10 minutes thanks to that 50 km/h wind. But the water temperature will never go below +2c, no matter how extreme the wind or windchill is. That's the effect of windchill. It describes an equivalent RATE OF COOLING, not an actual temperature. So if it's -20C with a -40 windchill, your car will likely still start if it's not plugged in because the battery will never get below -20C. On the other hand, if it's -40C with no windchill, your car will not start if it's not plugged in because the battery will cool off to -40C (given it's outside long enough). See the difference?

Before 2001, the Prairies used a windchill index that was given in watts/sq metre (e.g 1800 W/m2) This was a more scientifically valid measure of what windchill actually was.. a rate of cooling, expressed in the amount of energy loss in watts per square metre of area. However in 2001, the windchill was re-calculated and standardized for all of North America to the windchill index we use today, which was mainly based on the more common "equivalent temperature" index being used in Southern Ontario and the United States. A survey conducted at that time showed that most people found the watts/sq metre unit "too technical" a term to fully understand.

Saturday, December 12, 2009

For those of us starving for snow, take a look at some of the photos coming out of the Muskoka area in Ontario. Some extremely heavy lake effect snowsqualls off Georgian Bay over the past 2 days have left 100-150 cm of snow in some communities! Click on the photo for some amazing video out of MacTier.. south of Parry Sound. (photos and video posted to The Weather Network)

Friday, December 11, 2009

If you think it's cold out there, wait until this weekend. A bitterly cold Arctic airmass over northern SK will push into southern MB over the weekend, bringing even colder air along with bitter windchills to southern MB by Saturday evening into Sunday. Northwest winds will begin to increase Saturday afternoon, and increase up to 30 km/h Saturday night into Sunday. Temperatures will drop to the minus 30C mark Saturday night and only recover to the mid minus 20s on Sunday. Unlike the past week however, windchills will be more of a factor, with windchills in the minus 40 to minus 45 range Saturday night into Sunday. Brisk west winds and bitter windchills are expected to continue Monday into Tuesday.

Monday, December 07, 2009

A large Arctic ridge of high pressure has built into the western Prairies this morning, bringing the coldest weather of the season so far to much of the Prairies. Temperatures of -30 to -35C were widespread over Alberta and western SK this morning, including a record breaking -37C at Edmonton International. This Arctic ridge will settle over the southern Prairies today into Tuesday, bringing well below normal temperatures over the area. Afternoon highs will only be in the minus teens to -20 range over Winnipeg over the upcoming week, while nighttime lows drop into the -25 to -30 range. Minimum temperatures of -30 to -35 are likely over southwest MB over the next few nights. Get that block heater cord out!

Meanwhile a powerful blizzard is shaping up over the central US plains today, and will bring heavy snow and strong winds through Kansas, Nebraska, Iowa and southern Minnesota tonight into Tuesday.

Sunday, December 06, 2009

On this date in 1939, temperatures soared to a record December high of 11.7C in Winnipeg, the only time in Winnipeg climate history that a double digit temperature was reached in December. It was even warmer southwest of Winnipeg that day, with readings of up to 18C in places like Melita and Morden. Above normal temperatures and a lack of snow would stick around right into Christmas, leading to one of Winnipeg's only "green Christmases" ever recorded (the others were 1877, 1913, and 1997). Residents played golf, tennis and lawn bowling on Christmas day 1939 to take advantage of the snow free conditions.

Friday, December 04, 2009

Arctic air has finally moved into the Prairies, and an even colder surge of Arctic air will be pushing into the Prairies today through the weekend thanks to a strong area of high pressure building down from the Yukon. This second blast of Arctic air is currently pushing into Alberta with strong northerly winds, and snow and blowing snow giving near blizzard conditions through central and southern AB. This area of snow will push into the northern US, but the accompanying cold air will push across the eastern prairies over the weekend into early next week, bringing well below normal temperatures across southern MB. Look for highs in the minus teens by early next week with lows in the minus 25 to minus 30 range.

Wednesday, December 02, 2009

Colder weather is finally moving over southern Manitoba, ushered in by brisk northerly winds advecting colder Arctic air into the province for the first time in weeks. These winds are blowing over the still open waters of the Manitoba lakes, where ice formation has been delayed this year due to the prolonged mild weather in November. The result will be localized bands of lake effect snow off Lake Manitoba and Lake Winnipeg (particularly off the north basin). Northerly winds tonight and Thursday will set up snow bands immediately to the south of the lakes affecting areas through the central Interlake, as well as the Portage La Prairie and Beausejour areas. By Friday, the winds should veer slightly to the north-northwest which would push the snowbands a little further to the east. 10-20 cm of snow is possible under persistent snow bands while little snow is likely outside these areas. The cold weather is expected to persist for the next week or two, which will quickly freeze up the lakes over the next couple of weeks shutting down the lake effect machine.

After a rather chilly October, the weather pattern flipped in November to produce one of the mildest and driest Novembers on record in Winnipeg and southern Manitoba. Temperatures rose to above normal values on the 6th and stayed above normal every day through the end of the month. Winnipeg airport finished with a monthly mean temperature of +0.8C, the mildest November since 2001 (+0.9C) and the 5th mildest November since records began in 1872. Temperatures reached double digits on 10 days during the month, twice as many as October, and tying 1981 with the second most double digit days in November. In fact, the average daily high of +7.1C in November was just about the same as October (+7.3C) Combined with the warmest September on record, the 3 month fall period of Sep, Oct and Nov ended up tied with 1953 as the 4th mildest fall on record in Winnipeg with an average temperature of +7.3C. (Winnipeg's warmest fall was 1963 at 8.6C)

The big story however was the dryness of the month. Total precipitation at Winnipeg airport was only 1.5 mm .. tying 1901 and 1939 as the second driest November on record in Winnipeg (driest was 0.8 mm in 1976) All of the precipitation fell as melted snow with no rain during the month. The month was dominated by almost daily sunshine and mild temperature from the 4th to the 24th.. making it feel more like October than November. The extended fall weather and lack of snow allowed farmers to continue burning their fields well beyond the usual end date of Nov 15th.. requiring the province to extend the requirement for burning permits into December.

Tuesday, December 01, 2009

An Alberta clipper storm system is bringing an area of snow just south of Winnipeg this morning. Snow is falling from just south of the city to the US border, with the heaviest amounts across southwest MB into the southern Red River Valley. Radar indicates that 10-15 cm snow likely fell in a band from Virden to Morden (image left) overnight into this morning. Highways are snowcovered and slippery south and west of the city so be prepared for winter driving conditions if you are travelling south of the city today. This system will continue to slide southeastward today moving into northern Minnesota this afternoon. Gusty northwest winds behind this clipper will usher in colder air over all of southern MB tonight into Wednesday with temperatures finally returning to normal values for early December.